The aim of this study is to develop reliable and valid prevalence estimates of substance use among U.S. physicians as a whole, for major specialties, as well as for stages in the medical career ranging from residency training through late practice. This study will identify demographic, career development, and other risk factors for substance use, as well as adverse health and occupational experiences. It will assess the experience of physicians in obtaining help for themselves and their colleagues for problems of substance use. The data will be gathered in a cross-sectional prevalence survey of a stratified random sample of U.S. physicians in training and practice. One stratification variable will be year of graduation from medical school. Drug use patterns and associated variables will be examined for physicians at different stages in their medical careers, i.e., from residency training to mid-practice and pre- retirement practice. Medical school graduating classes of 1985, 1980, 1970, 1960, and 1950 will be sampled for this purpose. The second stratification variable is medical specialty. The eleven most common specialties, each of which represents at least two percent of total U.S. physicians, compose eleven strata. All other specialities will be collapsed into the twelfth stratum. This will permit the identification of specialties at high and low risk for particular substance use patterns, as well as drug availability and specialty-specific factors, that might help explain substance-related problems. The study was developed with the active support of the AMA Office of Education Research, and the sample will be drawn from the AMA Physician Masterfile. This close collaboration will be maintained throughout the study to assure that the results and recommendations which emerge will be relevant and have maximum impact on medical societies and concerned specialty organizations.